The present invention relates to a printed circuit board with an integral strain gage. Although the present invention addresses numerous problems, specific problems related to the manufacturing of printed circuit boards are discussed herein to provide a background of the invention.
During printed circuit board manufacturing, it is advantageous to measure strain associated with a printed circuit boards. Strain measurements can be used for stress analysis purposes. During the manufacturing processes printed circuit boards undergo a variety of operations that can be stressful. For example populating a board during one manufacturing operation may cause damage to connections made in a previous manufacturing operation. Locating and monitoring areas where strain is being produced on a printed circuit board is desirable. Knowledge regarding strain can be used to assess electronic component failure modes within a printed circuit board to thereby alter or improve the manufacturing process as necessary to reduce or eliminate defects and/or otherwise improve quality.
This problem has been addressed in the prior art by using conventional discrete strain gages attached to the surface of the printed circuit board with separate signal lead wires attached to the strain gage. In such an approach discrete strain gage sensors are glued to the top surface of the printed circuit board and attached to electrical circuitry via leadwires attached to the sensors.
In the case of prior art strain gages, there is a significant installation cost associated with placing a strain gage on a printed circuit board. This step is performed by a technician which is time-consuming and costly. This type of labor intensive installation process is not consistent with the goals of an automated assembly process or a high volume PCB manufacturing environment. Moreover, because an automated process is not used the results obtained from strain gages installed in this manner may not be as accurate or useful as desired due to inconsistencies between installations.
An alternative prior art approach has been to use strain-sensitive material applied by metal deposition directly to the board. This approach has allowed some use of printed circuit board manufacturing techniques, however there are significant disadvantages. In particular deposited metal does not provide the requisite strain-sensitive properties that may be required in more sensitive applications. Also, although printed circuit board manufacturing techniques are used, the use of a metal deposition step for the strain gage is a significant addition to the manufacturing process that may be cost prohibitive in particular applications.
A further problem is that with the prior art approaches there are numerous limitations as to where strain can be measured. Strain sensors can not be located in positions which are not readily accessible. Every place where it may be advantageous or appropriate to measure strain is simply not accessible with a discrete sensor.
Thus, despite these varying approaches used in the prior art, problems remain. Therefore, it is a primary object, feature or advantage of the present invention to improve upon the state of the art.
Another object, feature, or advantage of the present invention is to provide for accurately and efficiently locating areas of stress in a printed circuit board.
It is a further object, feature or advantage of the present invention to provide a printed circuit board with an integral strain gage as opposed to a discrete strain gage.
It is a still further object, feature or advantage of the present invention is to provide an integral strain gage that does not require deposition of material directly on the printed circuit board.
Another object, feature or advantage of the present invention is to provide an integral strain gage that is compatible with a multi-layer printed circuit board.
Yet another object, feature or advantage of the present invention is to provide an integral strain gage for use in a printed circuit board that allows for flexibility with respect to where in the printed circuit board the strain gage is placed.
A further object, feature or advantage of the present invention is to provide an integral strain gage that does not require using discrete sensors attached to the top surface of the printed circuit board.
A still further object, feature, or advantage of the present invention is to provide an integral strain gage in a printed circuit board suitable for transducer purposes such as measuring deflection or force.
Another object, feature, or advantage of the present invention is to provide an integral strain gage in a printed circuit board that is accurate.
One or more of these and/or other objects, features, or advantages of the present invention will become apparent from the specification and claims that follow.